5.1 This test method is used for determination of the carbon content of water from a variety of natural, domestic, and industrial sources. In its most common form, this test method is used to measure organic carbon as a means of monitoring organic pollutants in industrial wastewater. These measurements are also used in monitoring waste treatment processes.

5.2 The relationship of TOC to other water quality parameters such as chemical oxygen demand (COD) and total oxygen demand (TOD) is described in the literature.4

1.1 This test method covers the determination of total carbon (TC), inorganic carbon (IC), total organic carbon (TOC), dissolved organic carbon (DOC), and non-purgable organic carbon (NPOC) in water, wastewater, and seawater in the range from 0.5 mg/L to 4000 mg/L of carbon. Higher levels may be determined by sample dilution. The sample is injected onto a quartz bed heated at 680ºC. The sample converts into a gaseous phase and forced through a layer of catalyst ensuring conversion of all carbon containing compounds to CO₂. A non-dispersive infrared (NDIR) detector measures the resulting CO₂.

1.2 For TOC and DOC analysis a portion of the sample is injected to determine TC or dissolved carbon (DC). A portion of the sample is then acidified and purged to remove the IC. The purged inorganic carbon is measured as TIC, or DIC. TOC or DOC is calculated by subtracting the inorganic fraction from the total carbon:

1.3 For NPOC analysis a portion of sample is acidified and purged to remove IC. The purged sample is then injected to determine NPOC.

1.4 This test method was used successfully with reagent water spiked with potassium hydrogen phthalate, sucrose, nicotinic acid, benzoquinone, sodium dodecyl benzene sulfonate, urea, acetic acid, and humic acid. It is the user's responsibility to ensure the validity of this test method for waters of untested matrices.

1.5 This test method is applicable only to carbonaceous matter in the sample that can be introduced into the reaction zone. The syringe needle or injector opening size generally limits the maximum size of particles that can be so introduced.

1.6 In addition to laboratory analyses, this test method may be applied to stream monitoring.

1.7 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.

1.8 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.